As for an imaging technique capable of obtaining a distance in the depth direction as two-dimensional array information, various methods such as a method using a reference beam and a stereo distance measuring method using a plurality of cameras are being studied. Especially, in recent years, needs for comparatively inexpensive products as a new input device for consumer use have increased. In imaging apparatuses utilizing the light field photography technique, changeover between an ordinary imaging mode at high resolution which does not use the light field photography technique and an imaging mode based upon the light field photography technique is possible. In the former cited imaging mode, a microlens is not necessary. In the latter cited imaging mode, it is necessary to dispose a microlens on the optical axis.
The light field camera can be regarded as a camera in which the diaphragm mechanism in an ordinary camera is extended, and it is optically implemented by a multiview camera. In the light field camera, a plurality of images which are different in focal point are imaged simultaneously at various angles of view. An image which is in focus over the whole area can be generated by analyzing such image data. In addition, distance measurement utilizing the depth of field and estimation of the light source direction using an image data analysis can also be conducted, and information which cannot be obtained in the conventional cameras can also be acquired.
As a configuration in which multiple parallax images can be obtained and the resolution falling is suppressed, a multiview imaging apparatus having an image formation lens is proposed. This imaging apparatus includes an imaging lens, a macro lens array unit on which light transmitted by the imaging lens is incident, and an imaging device which receives light illuminated from the microlens array unit. Microlenses included in the microlens array unit are varifocal lenses in which the focal length becomes variable depending upon applied voltage.
As an example of the varifocal lens, a liquid crystal lens can be mentioned. In the liquid crystal lens, the apparent refractive index of the liquid crystal is changed by enclosing liquid crystal in a lens-shaped space and adjusting the applied voltage. Even if the lens has the same shape, the focal length of the lens is changed by changing the refractive index of a material which forms the lens.
If a liquid crystal lens is used as the varifocal lens, however, it becomes necessary to select special materials which implement a desired refractive index and a lens configuration which seals these materials becomes complicated, resulting in an increased manufacturing cost. Furthermore, the liquid crystal lens is susceptible to the influence of the environmental temperature and there is a fear that the focal length will change according to the ambient environmental temperature. In addition, it is difficult to conduct changeover for changing the focal length at high speed.